Diamond Cut Explained for Dummies

The cut grade of a diamond has nothing to do with its shape. It refers to the proportions, the polish and the symmetry of the stone. As the cut is perhaps the most important factor contributing the the beauty of a stone, one can’t compromise on it too much without getting a dull gem, without the lively brilliance that makes diamonds so sough after.

Why is the Cut of a Diamond so Crucial?

effects_of_an_excellent_diamond_cutThe cut has a direct influence on the brilliance, the fire and the scintillation of a diamond. The brilliance is the white light reflection through the crystal. The fire is the dispersion of the light that results in flashes of color covering the entire visible spectrum. The scintillation is the sparkle that appears when the diamond or the light source are moved. The combination of these three features makes a diamond awesome or less beautiful.

There’s a big pressure on diamond cutters to maintain as much carat weight as possible from the rough stone. The reason is that people are willing to pay more for a larger stone with a fair cut than for a smaller one with an excellent cut. This is a sacrifice that needs to be done in some situations. However, the cutter needs to know when to stop, as stones with a poor cut are far from being appealing. Besides, a smaller but very well cut diamond is going to have a higher price-per-carat than a larger, bot not so well cut one.

There are two reasons for this, the first one being that the appearance is much better in the first case. The second reason is that the yield from the raw stone is smaller, therefore making the diamond more expensive overall.

The miraculous effects of Excellent Diamond Proportions

The well proportioned gemstone will reflect about 20% of the incoming light off the surface. Out of the 80% entering the crystal, a certain percentage is going to pass through the bottom of the diamond, this meaning that nobody is going to appreciate it, since it isn’t visible to the eye of the observer. Go here for more details and you will quickly see why the exact proportions are so important!


The better the cut, the more amount of light is reflected back out of the crown of the diamond, to the eye of the viewer. A too shallow cut will allow too much light escape through the bottom of the stone, thus resulting in less brilliance. A too deep cut is also bad, because it causes the light to refract at the second pavilion, thus escaping through the bottom. The best cut is the one that determines the light to strike each facet at the perfect angle, sending most of the light back to the crown. There’s going to be some refraction upon exit, which is a good thing, as it generates the lively fire that makes diamonds so beautiful.

There are precise dimensions for each of the elements of a diamond. During the cut grading process, the stone is thoroughly measured. All results are represented on a proportion diagram, which is going to be the GIA Grading Report of that specific gemstone. All angles and dimensions are measured with a light scanning equipment. This diagram is the “fingerprint” of the diamond, and it is usually included with your purchase. The Cut grade is provided by the GIA, as it is isn’t easy to evaluate all combined effects of multiple facets, shapes and angles. Even professional gemologists may encounter difficulties in this type of endeavor. This is why the Cut grade provided by the GIA is universally accepted and taken into consideration when diamond prices are set.

The diamond cut is graded by measuring all the facets and the angles of the gem!